Sliver Vulnerable to Pre-Auth Memory Exhaustion via NoEncoder Bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.5 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary A specially crafted nonce routes unauthenticated requests through the NoEncoder path, where startSessionHandler() reads the entire request body without limits, allowing attacker-driven memory exhaustion and process crash. Details - server/encoders/encoders.go: EncoderFromNonce() returns NoEncoder when nonce % 65537 == 0 (lines 254-264); NoEncoder is a passthrough (util/encoders/nop.go:22-32). - server/c2/http.go: anonymousHandler() routes requests with any encoder (including NoEncoder) to startSessionHandler() (lines 551-562). - server/c2/http.go: startSessionHandler() uses io.ReadAll(req.Body) without a size cap (lines 564-643), unlike the authenticated path that uses io.LimitedReader (readReqBody(), lines 708-732). PoC An attacker could send an HTTP POST with a nonce that is a multiple of 65537 (e.g., ?q=65537) so it is handled by startSessionHandler() with a NoEncoder, and advertise a very large Content-Length while streaming data. Because this handler uses…

Published by the source

5 Jan 2026, 19:43 UTC

Last modified by the source

5 Jan 2026, 19:43 UTC

Source last checked

26 Oct 2026, 15:14 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hjr9-wj7v-7hv8

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# Patch Next advisory brief: GHSA-hjr9-wj7v-7hv8

Advisory: Sliver Vulnerable to Pre-Auth Memory Exhaustion via NoEncoder Bypass
IDs: GHSA-hjr9-wj7v-7hv8
Record: https://patchnext.com/advisories/ghsa-hjr9-wj7v-7hv8 (revision 1, source checked 26 Oct 2026, 15:14 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/bishopfox/sliver: affected >= 1.5.0, <= 1.5.44

## Suggested inspection (read-only)
- Go github.com/bishopfox/sliver: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/bishopfox/sliver.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hjr9-wj7v-7hv8 (GitHub-reviewed advisory GHSA-hjr9-wj7v-7hv8 lists affected ranges: Go github.com/bishopfox/sliver >=1.5.0 <=1.5.44)

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