# CVE-2026-77214: libexpat Heap Buffer Over-read in xmlparse.c via XML_ParseBuffer

> Heap buffer over-read in libexpat allows attackers to disclose adjacent heap memory, defeating ASLR and aiding further exploitation.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** ALPINE-CVE-2026-77214, AZL-106728, AZL-107228, BELL-CVE-2026-77214, CLSA-2026-1792993465, DEBIAN-CVE-2026-77214, ECHO-c50c-9d1f-aedb, GHSA-8xfx-9m5m-pgcp, OESA-2026-4348, OESA-2026-4349, OESA-2026-4350, OESA-2026-4351, RHSA-2026:77959, UBUNTU-CVE-2026-77214, openSUSE-SU-2026:12100-1

## What is CVE-2026-77214?

CVE-2026-77214 is a high-severity memory corruption vulnerability in libexpat, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

libexpat before commit 13c5f63 contains a heap buffer over-read vulnerability in xmlparse.c. XML_ParseBuffer advances the parse buffer end with parser->m_bufferEnd += len using a caller-supplied length that is not validated against the allocated buffer size, so repeated XML_ParseBuffer calls move m_bufferEnd past the end of the heap allocation and subsequent parsing reads out of bounds. Reaching this path requires a parse buffer to already be present; otherwise XML_ParseBuffer returns XML_ERROR_NO_BUFFER. A buffer is present after a prior call to XML_GetBuffer, either directly (the common case) or indirectly through a prior XML_Parse call that allocates the buffer internally. The over-read discloses adjacent heap memory to the calling application, recovering heap pointers, libc function pointers, and code pointers sufficient to defeat ASLR and build further exploitation primitives.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-77214?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `expat` | Red Hat:hummingbird:1 | All versions | 0:2.8.5-1.2.hum1 |
| `expat-devel` | Red Hat:hummingbird:1 | All versions | 0:2.8.5-1.2.hum1 |
| `expat-static` | Red Hat:hummingbird:1 | All versions | 0:2.8.5-1.2.hum1 |
| `expat` | openSUSE:Tumbleweed | All versions | 2.9.0-1.1 |

## How do I fix CVE-2026-77214?

Apply the vendor's patch.

## Is CVE-2026-77214 being exploited?

There is no known exploitation of CVE-2026-77214 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77214 and fix it if it is affected.

What it is: CVE-2026-77214 is a high-severity memory corruption vulnerability in libexpat, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77214 in the wild and no public exploit code.

Affected product: libexpat. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77214/ (Markdown: https://insights.sbomify.com/CVE-2026-77214/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77214
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77214
- OSV: https://osv.dev/vulnerability/CVE-2026-77214

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77214/
Summaries are generated and may contain mistakes; the official description above is the record.