CVE-2026-111497

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream. Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.

Summary

Out-of-bounds Write vulnerability in the bundled Brotli decoder in yjh0502 erl-brotli allows an attacker who supplies a crafted Brotli-compressed stream to brotli:decode/1 to corrupt decoder state memory, disclose memory contents, crash the Erlang VM, or potentially execute code.

erl-brotli compiles its own copy of the Google Brotli C sources under c_src into a NIF, and brotli_decoder_decompress_stream in c_src/brotli_nif.c hands the input to BrotliDecoderDecompressStream. In c_src/dec/decode.c, DecodeBlockTypeAndLength returns false for a block switch in a category with at most one block type, and the non-streaming callers DecodeLiteralBlockSwitch, DecodeCommandBlockSwitch and DecodeDistanceBlockSwitch discard that result, so decoding continues with inconsistent state. The decoder runs inside a NIF, so memory corruption or a crash takes down the whole VM rather than the calling process. Because the package carries its own copy of the library, the Brotli version installed on the host does not matter.

This issue affects brotli: from 0.3.0 before 0.3.4.

Impact

An attacker who can get an application to decode a Brotli stream they control, for example an HTTP client that decompresses Content-Encoding: br responses with this package, can crash the Erlang VM and potentially run code inside it.

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.

Brotli is a generic-purpose lossless compression algorithm that compresses data using a combination of a modern variant of the LZ77 algorithm, Huffman coding and 2nd order context modeling, with a compression ratio comparable to the best currently available general-purpose compression methods. It is similar in speed with deflate but offers more dense compression.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

Brotli is a generic-purpose lossless compression algorithm that compresses data using a combination of a modern variant of the LZ77 algorithm, Huffman coding and 2nd order context modeling, with a compression ratio comparable to the best currently available general-purpose compression methods. It is similar in speed with deflate but offers more dense compression.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

Brotli is a generic-purpose lossless compression algorithm that compresses data using a combination of a modern variant of the LZ77 algorithm, Huffman coding and 2nd order context modeling, with a compression ratio comparable to the best currently available general-purpose compression methods. It is similar in speed with deflate but offers more dense compression.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

Brotli is a generic-purpose lossless compression algorithm that compresses data using a combination of a modern variant of the LZ77 algorithm, Huffman coding and 2nd order context modeling, with a compression ratio comparable to the best currently available general-purpose compression methods. It is similar in speed with deflate but offers more dense compression.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

Python CFFI bindings to the Brotli library.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

Python CFFI bindings to the Brotli library.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

Python CFFI bindings to the Brotli library.

Security Fix(es):

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream.

Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.(CVE-2026-111497)

CVE-2026-111497 ("Node2Shell") is an out-of-bounds write (CWE-787) in Google's Brotli decoder (c/dec/decode.c). DecodeBlockTypeAndLength() returns an ambiguous value for an invalid block switch, and the fast decode path discards it (CWE-252, unchecked return value), so a crafted Brotli stream makes the decoder continue on corrupted state and write past the ring buffer. Upstream rates it CVSS 4.0 9.2 and classifies the impact as potential remote code execution.

The vulnerability is in Google's C library, not in Node.js specifically. The PyPI Brotli package is Google's CPython binding and compiles the same c/dec/decode.c that has the actual vulnerability. All Brotli releases up to and including 1.2.0 ship the vulnerable decoder; 1.2.1 contains the upstream fix (commit 0ed4268a) and differs from 1.2.0 only in that fix plus a version bump.

The decoder is reached whenever untrusted Brotli data is decompressed. With Brotli installed, common HTTP clients decode Brotli responses automatically (urllib3/requests, httpx with the brotli extra, aiohttp) and services that accept Content-Encoding: br request bodies decode inbound data, so the flaw is reachable from attacker-controlled input.

CVE-2026-111497 ("Node2Shell") is an out-of-bounds write (CWE-787) in Google's Brotli decoder (c/dec/decode.c). DecodeBlockTypeAndLength() returns an ambiguous value for an invalid block switch, and the fast decode path discards it (CWE-252, unchecked return value), so a crafted Brotli stream makes the decoder continue on corrupted state and write past the ring buffer. Upstream rates it CVSS 4.0 9.2 and classifies the impact as potential remote code execution.

The vulnerability is in Google's C library, not in Node.js specifically. The PyPI Brotli package is Google's CPython binding and compiles the same c/dec/decode.c that has the original vulnerability. All Brotli releases up to and including 1.2.0 ship the vulnerable decoder; 1.2.1 contains the upstream fix (commit 0ed4268a) and differs from 1.2.0 only in that fix plus a version bump.

The decoder is reached whenever untrusted Brotli data is decompressed. With brotlicffi installed, common HTTP clients decode Brotli responses automatically (urllib3/requests, httpx with the brotli extra, aiohttp) and services that accept Content-Encoding: br request bodies decode inbound data, so the flaw is reachable from attacker-controlled input.