How severe is GHSA-c279-989m-238f?

No CVSS score has been assigned to GHSA-c279-989m-238f yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-c279-989m-238f?

GHSA-c279-989m-238f affects the following packages: github.com/bishopfox/sliver (Go). Ecosystems affected: Go.

How do I fix GHSA-c279-989m-238f?

No patched version of github.com/bishopfox/sliver has shipped for GHSA-c279-989m-238f yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect GHSA-c279-989m-238f in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/bishopfox/sliver. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-c279-989m-238f if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-c279-989m-238f?

O3 pinpoints whether GHSA-c279-989m-238f is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-c279-989m-238f actively exploited in the wild?

No public exploit code has been indexed for GHSA-c279-989m-238f yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-c279-989m-238f published, and has it been updated?

GHSA-c279-989m-238f was published on March 29, 2026 and was last updated on April 2, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-c279-989m-238f

Sliver: Nil Pointer Dereference in tunnelCloseHandler causes panic when a reverse tunnel (rportfwd) close is attempted

Also known asGO-2026-4899

Published

Mar 29, 2026

Updated

Apr 2, 2026

Affected

1 pkg

Patched

None yet

Exploits

None indexed

Blast Radius

1 pkg affected

🐹github.com/bishopfox/sliver

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A nil pointer dereference in tunnelCloseHandler causes the handler goroutine to panic whenever a reverse tunnel (rportfwd) close is attempted. Both the legitimate close path AND the unauthorized close path dereference tunnel.SessionID where tunnel is guaranteed nil. This means rportfwd tunnels can never be cleanly closed, and any authenticated implant can trigger repeated goroutine panics.

Details

File: server/handlers/sessions.go lines 172 and 175

The function enters an else block precisely because core.Tunnels.Get(tunnelData.TunnelID) returned nil. Both conditions inside that else block then dereference tunnel.SessionID instead of rtunnel.SessionID:

} else {
    rtunnel := rtunnels.GetRTunnel(tunnelData.TunnelID)

    if rtunnel != nil && session.ID == tunnel.SessionID {      // LINE 172 — nil deref
        rtunnel.Close()
        rtunnels.RemoveRTunnel(rtunnel.ID)
    } else if rtunnel != nil && session.ID != tunnel.SessionID { // LINE 175 — nil deref
        sessionHandlerLog.Warnf("...")
    }
}

Note: The identical bug was already fixed in tunnelDataHandler at lines 124/126 (correctly uses rtunnel.SessionID), but the fix was not applied to tunnelCloseHandler.

PoC

tunnel := GetTunnel(999)   // returns nil — no normal tunnel with this ID
// tunnel is nil here

rtunnel := GetRTunnel(999) // returns valid rtunnel owned by session-AAAA

// Both lines below panic with:
// runtime error: invalid memory address or nil pointer dereference
if rtunnel != nil && sessionID == tunnel.SessionID { ... }      // line 172
} else if rtunnel != nil && sessionID != tunnel.SessionID { ... } // line 175

Confirmed on master commit 7ac4db3fa with standalone reproducer. Output:

PANIC on line 172 (legitimate close): runtime error: invalid memory address or nil pointer dereference
PANIC on line 175 (unauthorized close): runtime error: invalid memory address or nil pointer dereference

Impact

rportfwd tunnels cannot be closed — functional regression
Any authenticated implant can trigger repeated handler goroutine panics
rtunnel map entries leak (never cleaned up on close failure)
recoverAndLogPanic() prevents full server crash but silently drops the close operation

Fix

Replace tunnel.SessionID with rtunnel.SessionID on both lines:

-  if rtunnel != nil && session.ID == tunnel.SessionID {
+  if rtunnel != nil && session.ID == rtunnel.SessionID {
       rtunnel.Close()
       rtunnels.RemoveRTunnel(rtunnel.ID)
-  } else if rtunnel != nil && session.ID != tunnel.SessionID {
+  } else if rtunnel != nil && session.ID != rtunnel.SessionID {

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/bishopfox/sliver`	all versions	No fix

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/bishopfox/sliver. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of github.com/bishopfox/sliver has shipped for GHSA-c279-989m-238f yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-c279-989m-238f is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-c279-989m-238f. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary A nil pointer dereference in `tunnelCloseHandler` causes the handler goroutine to panic whenever a reverse tunnel (rportfwd) close is attempted. Both the legitimate close path AND the unauthorized close path dereference `tunnel.SessionID` where `tunnel` is guaranteed nil. This means rportfwd tunnels can never be cleanly closed, and any authenticated implant can trigger repeated goroutine panics. ### Details File: `server/handlers/sessions.go` lines 172 and 175 The function enters an `else` block precisely because `core.Tunnels.Get(tunnelData.TunnelID)` returned `nil`. Both condit

O3 Security · Impact-Aware SCA

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