Amazon Linux 2 (EOS) Security Advisory: ALAS2-2026-3970
Advisory Released Date: 2026-10-12
Advisory Updated Date: 2026-10-12
FAQs regarding Amazon Linux ALAS/CVE Severity
OOB Read via Integer Overflow on libsoup through libsoup/websocket/soup-websocket-connection.c via process_frame() leads to Undefined Behavior (CVE-2026-0716)
The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer overflow guard inside the if (masked) block, leaving unmasked server-to-client frames unprotected. A malicious WebSocket server can send a crafted unmasked frame with a payload length near UINT64_MAX to trigger an OOB read in a libsoup-based client when max_incoming_payload_size is set to 0. (CVE-2026-12478)
SoupAuthManager caches proxy authentication credentials without scoping them to the proxy authority (host:port). When the proxy configuration changes (e.g., via system settings or WPAD), cached Proxy-Authorization headers from the previous proxy are sent to the new proxy, leaking credentials. (CVE-2026-12547)
A heap out-of-bounds read flaw was found in libsoup. When parsing multipart HTTP messages, an integer type mismatch between the caller and soup_headers_parse() can cause the length parameter to be incorrectly truncated, leading to a heap buffer over-read. A remote attacker could use this flaw to crash an application using libsoup or potentially disclose heap memory contents. (CVE-2026-12548)
The fix for CVE-2026-2443 was regressed by a subsequent rework commit that replaced specific overflow checks with a general signed comparison. When a client sends a Range request with a suffix length exceeding the content size, the resulting negative start value is not properly clamped, leading to malformed HTTP 206 responses and log flooding. (CVE-2026-12549)
A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_read_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client application to crash or disclose sensitive heap memory. (CVE-2026-66337)
A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libsoup operates behind a strict frontend proxy, this parsing differential can be exploited to smuggle HTTP requests. (CVE-2026-66338)
A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel to the destination server. This allows the destination server to capture proxy credentials, leading to information disclosure. (CVE-2026-66339)
A flaw was found in libsoup's SoupServer HTTP Range header processing. The sort_ranges() comparator in soup-message-headers.c truncates a 64-bit subtraction result to 32-bit int, flipping the sign for range offsets differing by more than INT_MAX. This causes silent omission of requested byte ranges from HTTP 206 Partial Content responses on resources larger than approximately 2 GB. (CVE-2026-77014)
An algorithmic complexity flaw exists in libsoup's HTTP Range header processing that persists after the CVE-2025-32907 fix.
CVE-2025-32907 addressed memory amplification when a client repeated the same range many times in a single Range header. Commit 9bb92f7a corrected merge correctness in soup_message_headers_get_ranges_internal() in libsoup/soup-message-headers.c, but the coalescing loop still removes merged ranges using g_array_remove_index() for each coalesced element. Because GArray is contiguous, each mid-array removal performs an O(N) memmove. When many identical satisfiable ranges are supplied (for example bytes=0-0 repeated thousands of times), the loop performs O(N2) work coalescing them into a single range.
The vulnerable path is reachable server-side from handle_partial_get() in libsoup/server/http1/soup-server-message-io-http1.c when a SoupServer handler returns HTTP 200 with a non-empty body. No authentication is required. The number of ranges is bounded only by the maximum request header size (~100 KiB), allowing roughly 25,000 ranges per request. Reporter measurements on libsoup HEAD containing the CVE-2025-32907 fix show ~90 ms single-core CPU per such request at the wire maximum, blocking the server's event loop for that duration.
This is a CPU exhaustion / availability issue only. No memory corruption or information disclosure occurs.
Affected: libsoup versions containing the CVE-2025-32907 fix but not merge request !550.
Fixed upstream: MR !550 merged 2026-08-20, replacing per-element removal with O(N) in-place compaction and rejecting Range headers requesting more than 200 ranges.
Upstream report: https://gitlab.gnome.org/GNOME/libsoup/-/issues/538
Related: CVE-2025-32907 (CVE-2026-77680)
Affected Packages:
libsoup
Note:
This advisory is applicable to Amazon Linux 2 (AL2) Core repository. Visit this FAQ section for the difference between AL2 Core and AL2 Extras advisories.
Issue Correction:
Run yum update libsoup or yum update --advisory ALAS2-2026-3970 to update your system.
aarch64:
libsoup-2.56.0-6.amzn2.0.9.aarch64
libsoup-devel-2.56.0-6.amzn2.0.9.aarch64
libsoup-debuginfo-2.56.0-6.amzn2.0.9.aarch64
i686:
libsoup-2.56.0-6.amzn2.0.9.i686
libsoup-devel-2.56.0-6.amzn2.0.9.i686
libsoup-debuginfo-2.56.0-6.amzn2.0.9.i686
src:
libsoup-2.56.0-6.amzn2.0.9.src
x86_64:
libsoup-2.56.0-6.amzn2.0.9.x86_64
libsoup-devel-2.56.0-6.amzn2.0.9.x86_64
libsoup-debuginfo-2.56.0-6.amzn2.0.9.x86_64