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.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 1.7.6
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.7.6.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 25/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- 1 proof of concept on GitHub
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.
Read the original 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.2/10CVSS 8.2
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
- Would score about 30 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 1.7.6.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- BishopFox sliver
fixed in 1.7.6
Evidence 4
- Advisory
- Exploit
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-77622
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: cve.now feed data
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: github.com
Which versions are affected by CVE-2026-77622?
sliver: before 1.7.6.Source: cve.now feed data
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: github.com
How do I fix CVE-2026-77622?
Upgrade Sliver to 1.7.6 or later, which is the listed fixed version.Source: github.com