ALAS2027-2026-305

References: CVE-2026-78659  CVE-2026-78667  CVE-2026-92542  CVE-2026-92543  CVE-2026-93318  CVE-2026-93320  CVE-2026-93450 
FAQs regarding Amazon Linux ALAS/CVE Severity

Issue Overview:

Package updates are available for Amazon Linux 2027 that fix the following vulnerabilities:
CVE-2026-93450:
go-openapi/swag jsonutils before 0.27.1 contains a stack overflow vulnerability in ordered JSON parsing and serialization due to unbounded recursion with no depth limit. Remote unauthenticated attackers can submit deeply nested JSON documents to services accepting OpenAPI specifications, causing fatal stack overflow that terminates the process and all in-flight requests.

CVE-2026-93320:
BuildKit may be tricked into performing file actions with special file inodes where regular files are expected. Special files may block operations or, on rootful workers, allow unintended host device access.

CVE-2026-93318:
A malicious image can advertise DiffIDs from another image while containing different layer contents. In affected versions, BuildKit could use the advertised DiffIDs to derive cache and snapshot identity without validating that they matched the actual layer contents.

If a BuildKit daemon with shared or persistent cache first processes such a malicious image, a later build using the victim image may mount the attacker-controlled layer contents as the base image. This can allow code from the malicious image to run in the victim build, for example by replacing a commonly executed path such as /bin/sh. The attacker-controlled code may read build secrets mounted into the build, access other build resources, alter output artifacts, or hang the build.

The issue affects both regular snapshotters and lazy-pulling snapshotters such as stargz.

CVE-2026-92543:
Docker Engine classifies a registry hostname as insecure using an any-match DNS check. loadInsecureRegistries() injects 127.0.0.0/8 and ::1/128 as insecure CIDRs by default. isCIDRMatch resolves all of the hostname's addresses and returns true if a single address is in the insecure CIDR list. Because the transport re-dials the hostname rather than the CIDR-matching address, a DNS answer set of one loopback IP plus a non-loopback attacker IP disables certificate verification and enables HTTP fallback for the registry connection.

CVE-2026-92542:
The firewall rules which mark VXLAN datagrams for encryption indiscriminately match both authentic VXLAN datagrams sent from the kernel and forged datagrams sent by user processes. Any packet sent from the host network namespace of a Linux Swarm node is encrypted with the overlay-network IPsec parameters which meets the following criteria:

- UDP datagram
- Destination port is the Swarm data-path port
- Datagram starts with a VXLAN header for the VNI of an encrypted overlay network which any running container on the node is connected to

CVE-2026-78667:
When parsing a Range header containing a large number of small ranges, FileServer(FS), ServeContent, and ServeFile(FS) could consume an excessive amount of CPU.

These functions now ignore Range headers containing more than 200 ranges.
The limit is controlled by the new httpservecontentmaxranges=GODEBUG setting. Setting GODEBUG=httpservecontentmaxranges=0 disables the limit.

NOTE: https://www.openwall.com/lists/oss-security/2026/10/08/9
NOTE: https://github.com/golang/go/issues/81858
NOTE: Fixed by: https://github.com/golang/go/commit/ababc3cd873d8acce1777268aa7a817e6b672028 (go1.27.2)
NOTE: Fixed by: https://github.com/golang/go/commit/eb25b4e532c5a01f99ef860ec66743a8783f992b (go1.26.9)

CVE-2026-78659:
When "Trailer" headers are sent by a client, the HTTP server internally uses the header values to populate the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs memory overhead. For HTTP/2 servers, a malicious client can exploit this by sending a "Trailer" header that declares a large number of fields causing the server to allocate a disproportionate amount of memory while bypassing Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits.
This exploit is not applicable for HTTP/1 servers, which do not support multiplexing a large number of requests over one TCP connection, and whose Server.MaxHeaderBytes are calculated differently.
Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits are now applied towards the trailer fields declared in "Trailer" headers.

NOTE: https://www.openwall.com/lists/oss-security/2026/10/08/9
NOTE: https://github.com/golang/go/issues/81857
NOTE: Fixed by: https://github.com/golang/go/commit/cbb0fb8b51cba866018b8a0fb4b5458f16c5c80b (go1.27.2)
NOTE: Fixed by: https://github.com/golang/go/commit/6e049521882c944afc1e519a83971ec421dc2974 (go1.26.9)

Issue Correction:
Run dnf update docker --releasever 2027.0.20261102 or dnf update --advisory ALAS2027-2026-305 --releasever 2027.0.20261102 to update your system.

New Packages:

aarch64:
    docker-debuginfo-29.9.1-1.amzn2027.0.1.aarch64
    docker-29.9.1-1.amzn2027.0.1.aarch64
    docker-debugsource-29.9.1-1.amzn2027.0.1.aarch64

src:
    docker-29.9.1-1.amzn2027.0.1.src

x86_64:
    docker-debuginfo-29.9.1-1.amzn2027.0.1.x86_64
    docker-29.9.1-1.amzn2027.0.1.x86_64
    docker-debugsource-29.9.1-1.amzn2027.0.1.x86_64