zstd-jni: Use After Free
CVE-2026-87877 is a high-severity use after free vulnerability in zstd-jni from Luben, with a CVSS 3.1 base score of 7.7 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists version 1.5.7-14 as the first without the flaw, so updating zstd-jni to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.22% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update zstd-jni to 1.5.7-14 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Luben | zstd-jni | 1.3.8-4 up to, but not including, 1.5.7-14 | 1.5.7-14 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 7.0 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 7.7 | High | CNA (vulncheck.com) |
Official description
zstd-jni versions before 1.5.7-14 fail to validate closed state in setDict, setLongMax, setLevel and setRefMultipleDDicts methods of stream classes. Attackers can call these methods on closed streams to write through freed native pointers, corrupting unrelated objects or crashing the JVM.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
References
Patches and release notes
Other references
- github.com/luben/zstd-jni
- github.com/luben/zstd-jni/blob/v1.5.7-13/src/main/java/com/github/luben/zstd/BaseZstdBufferDecompressingStrea…
- github.com/luben/zstd-jni/blob/v1.5.7-13/src/main/java/com/github/luben/zstd/ZstdInputStreamNoFinalizer.java
- vulncheck.com/advisories/zstd-jni-1.3.8-4-through-1.5.7-13-use-after-free-via-setters-called-after-close
Other vulnerabilities in zstd-jni
- 7.3 High severity
- 8.2 High severity
- 8.2 High severity
- 7.7 High severity
- 7.5 High severity
- 8.2 High severity
Recent Use After Free vulnerabilities
- 8.3 High severity
- 9.6 Critical severity
- 8.3 High severity
- 9.6 Critical severity
- 9.6 Critical severity
- 8.6 High severity
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