# What is CVE-2021-26291?

> CVE-2021-26291 is a critical-severity flaw (CVSS 9.1) in Maven from Apache, published on 23 April 2021. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 8.7%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-26291

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 52 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** Critical (CVSS 9.1 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 8.7% (latest exploit-likelihood forecast)
- **Published:** 23 April 2021
- **Record last updated:** 7 November 2023
- **Main product:** Maven from Apache
- **Affected products:** 4

## What is CVE-2021-26291? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data and change data.

### The official description

Apache Maven will follow repositories that are defined in a dependency’s Project Object Model (pom) which may be surprising to some users, resulting in potential risk if a malicious actor takes over that repository or is able to insert themselves into a position to pretend to be that repository. Maven is changing the default behavior in 3.8.1+ to no longer follow http (non-SSL) repository references by default. More details available in the referenced urls. If you are currently using a repository manager to govern the repositories used by your builds, you are unaffected by the risks present in the legacy behavior, and are unaffected by this vulnerability and change to default behavior. See this link for more information about repository management: https://maven.apache.org/repository-management.html

### What kind of flaw is it?

- CWE-346: Origin Validation Error

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Easy: no special conditions
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can read data and change data

Severity vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`

## Is CVE-2021-26291 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 8.7%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 8.7%, 8.7%, 8.7%, 8.7%, 8.7%, 8.7%, 8.7%.

### Timeline

- 23 April 2021: Published
- 7 November 2023: Record last updated
- 19 November 2025: Exploit likelihood fell
- 22 November 2025: Exploit likelihood jumped

### How Precursor Intelligence ranks it

CVE-2021-26291 scores **52 out of 100 (Medium)**, with the action "Plan remediation".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2021-26291?

The published record lists 4 products. Versions are as published: "before 3.8.1" means every version up to, but not including, 3.8.1.

- [Maven](https://www.precursorintelligence.com/product/apache/maven) by [Apache](https://www.precursorintelligence.com/vendors/apache) (Application): before 3.8.1
- [Financial Services Analytical Applications Infrastructure](https://www.precursorintelligence.com/product/oracle/financial_services_analytical_applications_infrastructure) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.0.6.0.0 to 8.0.9.0.0, 8.1.0.0.0 to 8.1.2.0
- [Goldengate Big Data and Application Adapters](https://www.precursorintelligence.com/product/oracle/goldengate_big_data_and_application_adapters) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 23.1
- [Quarkus](https://www.precursorintelligence.com/product/quarkus/quarkus) by [Quarkus](https://www.precursorintelligence.com/vendors/quarkus) (Application): before 1.13.5

## How do I fix CVE-2021-26291?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [oracle.com](https://www.oracle.com/security-alerts/cpuapr2022.html) (Patch, Third-party advisory)
- [lists.apache.org](https://lists.apache.org/thread.html/r9a027668558264c4897633e66bcb7784099fdec9f9b22c38c2442f00%40%3Cusers.maven.apache.org%3E) (Mailing list, Vendor advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2021/04/23/5) (Mailing list, Third-party advisory)
- [lists.apache.org](https://lists.apache.org/thread.html/r0556ce5db7231025785477739ee416b169d8aff5ee9bac7854d64736%40%3Cannounce.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r06db4057b74e0598a412734f693a34a8836ac6f06d16d139e5e1027c%40%3Cdev.maven.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r07a89b32783f73bda6903c1f9aadeb859e5bef0a4daed6d87db8e4a9%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r08a401f8c98a99f68d061fde6e6659d695f28d60fe4f0413bcb355b0%40%3Ccommits.druid.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r0a5e4ff2a7ca7ad8595d7683afbaeb3b8788ba974681907f97e7dc8e%40%3Cjira.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r0d083314aa3934dd4b6e6970d1f6ee50f6eaa9d867deb2cd96788478%40%3Cjira.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r167dbc42ef7c59802c2ca1ac14735ef9cf687c25208229993d6206fe%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r2721aba31a8562639c4b937150897e24f78f747cdbda8641c0f659fe%40%3Cusers.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r2ddabd06d94b60cfb0141e4abb23201c628ab925e30742f61a04d013%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r30a139c165b3da6e0d5536434ab1550534011b1fdfcd2f5d95892c5b%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r30e9fcba679d164158cc26236704c351954909c18cb2485d11038aa6%40%3Cdev.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r340e75c9bb6e8661b89e1cf2c52f4638a18312e57bd884722bc28f52%40%3Cjira.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r39fa6ec4b7e912d3e04ea68efd23e554ec9c8efa2c96f5b45104fc61%40%3Cjira.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r3f0450dcab7e63b5f233ccfbc6fca5f1867a75c8aa2493ea82732381%40%3Cdev.jena.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r4e1619cfefcd031fac62064a3858f5c9229eef907bd5d8ef14c594fc%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r52c6cda14dc6315dc79e72d30109f4589e9c6300ef6dc1a019da32d4%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r53cd5de57aaa126038c5301d8f518f3defab3c5b1c7e17c97bad08d8%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r5ae6aaa8a2ce86145225c3516bb45d315c0454e3765d651527e5df8a%40%3Ccommits.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r71bc13669be84c2ff45b74a67929bc2da905c152e12a39b406e3c2a0%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r7212b874e575e59d648980d91bc22e684906aee9b211ab92da9591f5%40%3Cdev.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r74329c671df713f61ae4620ee2452a0443ccad7f33c60e8ed7d21ff9%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r77af3ac7c3bfbd5454546e13faf7aec21d627bdcf36c9ca240436b94%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r78fb6d2cf0ca332cfa43abd4471e75fa6c517ed9cdfcb950bff48d40%40%3Cjira.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r86aebd0387ae19b740b3eb28bad83fe6aceca0d6257eaa810a6e0002%40%3Ccommits.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r86e1c81e03f441855f127980e9b3d41939d04a7caea2b7ab718e2288%40%3Cjira.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/r96cc126d3ee9aa42af9d3bb4baa94828b0a5f656584a50dcc594125f%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/ra88a0eba7f84658cefcecc0143fd8bbad52c229ee5dfcbfdde7b6457%40%3Cdev.jena.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/ra9d984eccfd2ae7726671e025f0296bf03786e5cdf872138110ac29b%40%3Ccommits.druid.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rc7ae2530063d1cd1cf8e9fa130d10940760f927168d4063d23b8cd0a%40%3Ccommits.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rc9e441c1576bdc4375d32526d5cf457226928e9c87b9f54ded26271c%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rcd37d9214b08067a2e8f2b5b4fd123a1f8cb6008698d11ef44028c21%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rcd6c3a36f1dbc130da1b89d0f320db7040de71661a512695a8d513ac%40%3Cdev.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rdcbad6d8ce72c79827ed8c635f9a62dd919bb21c94a0b64cab2efc31%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/re75f8b3dbc5faa1640908f87e644d373e00f8b4e6ba3e2ba4bd2c80b%40%3Ccommits.druid.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/red3bf6cbfd99e36b0c0a4fa1cea1eef1eb300c6bd8f372f497341265%40%3Cdev.kafka.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rf9abfc0223747a56694825c050cc6b66627a293a32ea926b3de22402%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rfc0db1f3c375087e69a239f9284ded72d04fbb55849eadde58fa9dc2%40%3Cissues.karaf.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rfc27e2727a20a574f39273e0432aa97486a332f9b3068f6ac1346594%40%3Cdev.myfaces.apache.org%3E)
- [oracle.com](https://www.oracle.com/security-alerts/cpujul2022.html)
- [whitesourcesoftware.com](https://www.whitesourcesoftware.com/resources/blog/maven-security-vulnerability-cve-2021-26291/) (Exploit, Third-party advisory)

## Questions

### What is CVE-2021-26291?

CVE-2021-26291 is a critical-severity flaw in Maven from Apache, published on 23 April 2021. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data and change data.

### How serious is CVE-2021-26291?

It scores 9.1 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2021-26291 is 52 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2021-26291 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 8.7%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2021-26291 affect?

For Maven from Apache: before 3.8.1. The record lists 4 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2021-26291?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2021-26291 affect you?

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- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
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