Red Hat Security Advisory: osbuild-composer security update

Fixed packages 16

Vulnerabilities 17

• Critical 9.6
  CVE-2026-39821

  Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna

  The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege …

  Go standard library golang.org/x/net net/http net/http/internal/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  May 22, 2026
• Critical 9.1
  CVE-2025-68121

  Unexpected session resumption in crypto/tls

  During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between the initial handshake and the resumed handshake, the resumed handshake may succeed when it should have failed. This may happen when a user ca…

  Go standard library crypto/tls langfuse-3-worker katib-suggestion-hyperopt Debian Ubuntu Azure Linux Alpine Wolfi Go
  Feb 5, 2026
• High 7.5
  CVE-2026-32280

  Unexpected work during chain building in crypto/x509

  During chain building, the amount of work that is done is not correctly limited when a large number of intermediate certificates are passed in VerifyOptions.Intermediates, which can lead to a denial of service. This affects both direct users of crypto/x509 an…

  Go standard library crypto/x509 golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Apr 8, 2026
• High 7.5
  CVE-2026-32281

  Inefficient policy validation in crypto/x509

  Validating certificate chains which use policies is unexpectedly inefficient when certificates in the chain contain a very large number of policy mappings, possibly causing denial of service. This only affects validation of otherwise trusted certificate chain…

  Go standard library crypto/x509 golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Apr 8, 2026
• High 7.5
  CVE-2026-33810

  Case-sensitive excludedSubtrees name constraints cause Auth Bypass in crypto/x509

  When verifying a certificate chain containing excluded DNS constraints, these constraints are not correctly applied to wildcard DNS SANs which use a different case than the constraint. This only affects validation of otherwise trusted certificate chains, issu…

  Go standard library crypto/x509 golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Apr 8, 2026
• High 7.5
  CVE-2026-33818

  Enforce maximum recursion depth in encoding/asn1

  Enforce a recursion limit in Unmarshal to prevent stack exhaustion when parsing deeply-nested, recursive structures.

  Go standard library encoding/asn1 katib-suggestion-hyperopt katib-suggestion-goptuna-compat Debian Ubuntu Azure Linux Alpine Wolfi Go
  Aug 13, 2026
• High 7.5
  CVE-2026-42504

  Quadratic complexity in WordDecoder.DecodeHeader in mime

  Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.

  Go standard library mime golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Jun 2, 2026
• High 7.5
  CVE-2026-55677

  Echo: Encoded slash (%2F) bypasses route-level protection and exposes static files

  Echo is a Go web framework. Prior to 4.15.3 and 5.2.0, Echo's router and static file handler disagree on URL path decoding. The router matches routes using the raw encoded path (preserving %2F as-is), while StaticDirectoryHandler unescapes %2F to / before res…

  labstack echo temporal temporal-ui-server Debian Ubuntu Wolfi Go
  Jun 26, 2026
• High 7.5
  CVE-2026-56853

  Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http

  When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this.

  Go standard library net/http golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Aug 13, 2026
• High 7.5
  CVE-2026-56859

  Add recursion depth guard during decode in encoding/xml

  Previously, DecodeElement would reset the depth counter causing it to never fire; this could lead to stack exhaustion.

  Go standard library encoding/xml golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Aug 13, 2026
• High 7.5
  CVE-2026-56862

  Limit handshake messages we are willing to accept post-handshake in crypto/tls

  Handshake messages, such as KeyUpdate, are always considered as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key deriva…

  Go standard library crypto/tls golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Aug 13, 2026
• High 7.5
  CVE-2026-78667

  Lack of limit on size of parsed Range headers in net/http

  When parsing a Range header containing a large number of small ranges, FileServer(FS), ServeContent, and ServeFile(FS) can consume an excessive amount of CPU.

  Go standard library net/http golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-78669

  Excessive CPU consumption from repeated initial window changes in net/http

  A malicious HTTP/2 peer can cause excessive CPU consumption in the client or server by opening a large number of streams and then sending many small SETTINGS frames containing SETTINGS_INITIAL_WINDOW_SIZE values.

  Go standard library golang.org/x/net net/http golang.org/x/net/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-94440

  Memory limit bypass when parsing MIME headers in net/textproto, mime/multipart

  Parsing a multipart form can bypass memory limits and read an arbitrarily long line into memory when the remaining limit at the start of a part is less than 400 bytes.

  Go standard library net/textproto mime/multipart golang Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-97031

  Reject malformed ECH outer extension references in crypto/tls

  Multiple ECH outer extension references are not permitted under RFC 9849; previously, a client could send a well-crafted packet that could trigger memory exhaustion in the server process by specifying multiple references. We now reject these as malformed and …

  Go standard library crypto/tls golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• Medium 6.1
  CVE-2026-56858

  Fix Javascript regexp context tracking in html/template

  Previously, pathological inputs could close an unescaped '/' early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS.

  Go standard library html/template katib-suggestion-hyperopt katib-suggestion-goptuna-compat Debian Ubuntu Azure Linux Alpine Wolfi Go
  Aug 13, 2026
• Medium 5.9
  CVE-2026-56860

  Avoid quadratic complexity in resolvePath in net/url

  Previously, resolving relative paths containing parent directory ('..') segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead. Now, path resolution operates on a byte…

  Go standard library net/url katib-suggestion-hyperopt katib-suggestion-goptuna-compat Debian Ubuntu Azure Linux Alpine Wolfi Go
  Aug 13, 2026

References

• article
  https://access.redhat.com/security/updates/classification/#important
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2437111
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2456333
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2456335
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2456339
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2480756
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2484204
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2493622
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2515815
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2515820
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2515827
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2515838
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2515839
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2515840
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548334
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548336
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548341
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548344
• advisory
  https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_96076.json
• report
  https://access.redhat.com/security/cve/CVE-2025-68121
• advisory
  https://www.cve.org/CVERecord?id=CVE-2025-68121
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2025-68121
• article
  https://go.dev/cl/737700
• article
  https://go.dev/issue/77217
• article
  https://groups.google.com/g/golang-announce/c/K09ubi9FQFk
• advisory
  https://pkg.go.dev/vuln/GO-2026-4337
• report
  https://access.redhat.com/security/cve/CVE-2026-32280
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-32280
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-32280
• article
  https://go.dev/cl/758320
• article
  https://go.dev/issue/78282
• article
  https://groups.google.com/g/golang-announce/c/0uYbvbPZRWU
• advisory
  https://pkg.go.dev/vuln/GO-2026-4947
• report
  https://access.redhat.com/security/cve/CVE-2026-32281
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-32281
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-32281
• article
  https://go.dev/cl/758061
• article
  https://go.dev/issue/78281
• advisory
  https://pkg.go.dev/vuln/GO-2026-4946