CVE-2026-58152: Apache Traffic Server Buffer Overflow

CVE-2026-58152 Overview

CVE-2026-58152 affects Apache Traffic Server (ATS), a high-performance HTTP proxy and caching server. The flaw involves improper integer handling during HPACK and XPACK header decoding, which corrupts memory. HPACK is the header compression format used by HTTP/2, while XPACK covers the QPACK/HPACK variants used across HTTP/3 and related protocols. The issue is classified as an integer overflow or wraparound [CWE-190]. Remote attackers can send crafted compressed headers to trigger the memory corruption without authentication or user interaction.

Critical Impact
Unauthenticated network attackers can corrupt memory in Apache Traffic Server by sending crafted HPACK or XPACK headers, impacting integrity and availability of the proxy service.

Affected Products

Apache Traffic Server 8.0.0 through 8.1.9
Apache Traffic Server 9.0.0 through 9.2.14
Apache Traffic Server 10.0.0 through 10.1.3

Discovery Timeline

2026-07-29 - CVE-2026-58152 published to NVD
2026-07-30 - Last updated in NVD database

Technical Details for CVE-2026-58152

Vulnerability Analysis

Apache Traffic Server decodes compressed HTTP headers using HPACK for HTTP/2 and XPACK for related HTTP/3 header compression flows. During integer decoding within these formats, the server mishandles values, producing arithmetic conditions that lead to memory corruption. An attacker who can reach the proxy over the network can deliver malformed integer sequences inside header frames. The result is corruption of adjacent memory regions used by the header decoder.

The flaw is remotely triggerable without authentication or user interaction. Impact is limited to partial integrity and availability effects rather than confidentiality loss. In practice, this maps to conditions such as decoder state corruption, request smuggling adjacent to header parsing, or process instability.

Root Cause

The root cause is an integer overflow or wraparound during variable-length integer decoding in the HPACK and XPACK header codecs [CWE-190]. HPACK and XPACK encode integers using a prefix-plus-continuation scheme in which each continuation byte contributes seven bits, shifted by an increasing power of two. Without strict bounds checking on the accumulator or shift amount, adversary-controlled inputs cause the value to wrap or exceed intended limits, resulting in undersized allocations or out-of-bounds writes during header expansion.

Attack Vector

Exploitation requires only network access to the Traffic Server proxy on ports handling HTTP/2 or HTTP/3 traffic. The attacker establishes a session and transmits a crafted HEADERS frame or equivalent QPACK-encoded frame containing malformed integer fields. The decoder processes the crafted sequence, triggers the integer error, and corrupts memory tied to the header table or decoding buffers. No prior credentials or user interaction are required.

The vulnerability mechanism is documented in the Apache Security Discussion. No public proof-of-concept exploit code is currently available.

Detection Methods for CVE-2026-58152

Indicators of Compromise

Unexpected traffic_server process crashes, restarts, or coredumps correlated with inbound HTTP/2 or HTTP/3 sessions.
Log entries in diags.log or error.log referencing HPACK, XPACK, or QPACK decoding failures and protocol errors.
Sudden spikes in HTTP/2 GOAWAY frames or HTTP/3 H3_FRAME_ERROR responses issued by the proxy.
Anomalous inbound HEADERS frames with oversized or malformed variable-length integer fields.

Detection Strategies

Inspect HTTP/2 and HTTP/3 traffic at the network layer for malformed HPACK/XPACK integer encodings exceeding reasonable bounds.
Monitor Apache Traffic Server versions in inventory and flag any host running 8.0.0–8.1.9, 9.0.0–9.2.14, or 10.0.0–10.1.3.
Correlate proxy process termination events with recent client sessions to identify potential exploitation attempts.

Monitoring Recommendations

Forward Traffic Server diagnostic and access logs to a centralized SIEM for parsing of protocol error events.
Enable core dump collection on Traffic Server hosts to support post-incident analysis of memory corruption.
Track EPSS score of 0.231% and revise monitoring priority if exploit availability changes.

How to Mitigate CVE-2026-58152

Immediate Actions Required

Upgrade Apache Traffic Server to version 9.2.15 or 10.1.4, which contain the fix from the maintainers.
Identify all Traffic Server instances in the affected 8.x, 9.x, and 10.x ranges and prioritize internet-facing nodes.
Review recent proxy logs for the indicators listed above to determine whether exploitation has been attempted.

Patch Information

The Apache Traffic Server project released fixed versions 9.2.15 and 10.1.4. Version 8.x is no longer supported by the fix set, so operators on the 8.0.0–8.1.9 branch must migrate to a supported release. Details are available in the Apache Security Discussion.

Workarounds

Restrict inbound HTTP/2 and HTTP/3 access to Traffic Server from untrusted networks where feasible.
Terminate HTTP/2 and HTTP/3 at an upstream load balancer that enforces strict header validation until patching completes.
Disable HTTP/2 and HTTP/3 listeners in records.yaml or records.config if the deployment can tolerate HTTP/1.1-only operation.

bash

# Verify installed version and upgrade path
traffic_server --version

# Example upgrade using distribution package manager
sudo systemctl stop trafficserver
sudo apt-get update && sudo apt-get install --only-upgrade trafficserver
# Confirm version is 9.2.15 or 10.1.4
traffic_server --version
sudo systemctl start trafficserver