diff --git a/models/issues/comment.go b/models/issues/comment.go
index 9dd2ca23837..02de587fb25 100644
--- a/models/issues/comment.go
+++ b/models/issues/comment.go
@@ -34,6 +34,7 @@ import (
 	"gitea.dev/modules/util"
 
 	"xorm.io/builder"
+	"xorm.io/xorm"
 )
 
 // ErrCommentNotExist represents a "CommentNotExist" kind of error.
@@ -398,12 +399,19 @@ func (c *Comment) LoadIssue(ctx context.Context) (err error) {
 	return err
 }
 
+var (
+	_ xorm.BeforeInsertProcessor = (*Comment)(nil)
+	_ xorm.BeforeUpdateProcessor = (*Comment)(nil)
+)
+
 // BeforeInsert will be invoked by XORM before inserting a record
 func (c *Comment) BeforeInsert() {
 	c.PatchQuoted = c.Patch
 	if !utf8.ValidString(c.Patch) {
 		c.PatchQuoted = strconv.Quote(c.Patch)
 	}
+
+	sanitizeDatabaseStringContent(&c.Content)
 }
 
 // BeforeUpdate will be invoked by XORM before updating a record
@@ -412,6 +420,8 @@ func (c *Comment) BeforeUpdate() {
 	if !utf8.ValidString(c.Patch) {
 		c.PatchQuoted = strconv.Quote(c.Patch)
 	}
+
+	sanitizeDatabaseStringContent(&c.Content)
 }
 
 // AfterLoad is invoked from XORM after setting the values of all fields of this object.
diff --git a/models/issues/issue.go b/models/issues/issue.go
index 0ce15737f75..fb3803010e0 100644
--- a/models/issues/issue.go
+++ b/models/issues/issue.go
@@ -11,6 +11,7 @@ import (
 	"regexp"
 	"slices"
 	"strconv"
+	"strings"
 
 	"gitea.dev/models/db"
 	project_model "gitea.dev/models/project"
@@ -25,6 +26,7 @@ import (
 	"gitea.dev/modules/util"
 
 	"xorm.io/builder"
+	"xorm.io/xorm"
 )
 
 // ErrIssueNotExist represents a "IssueNotExist" kind of error.
@@ -123,6 +125,27 @@ func init() {
 	db.RegisterModel(new(IssueIndex))
 }
 
+func sanitizeDatabaseStringContent(s *string) {
+	// postgresql doesn't like "\x00"
+	// this is only a simple workaround for issues like https://github.com/go-gitea/gitea/issues/28890 and https://github.com/go-gitea/gitea/issues/40003
+	*s = strings.ReplaceAll(*s, "\x00", " ")
+}
+
+var (
+	_ xorm.BeforeInsertProcessor = (*Issue)(nil)
+	_ xorm.BeforeUpdateProcessor = (*Issue)(nil)
+)
+
+func (issue *Issue) BeforeInsert() {
+	sanitizeDatabaseStringContent(&issue.Title)
+	sanitizeDatabaseStringContent(&issue.Content)
+}
+
+func (issue *Issue) BeforeUpdate() {
+	sanitizeDatabaseStringContent(&issue.Title)
+	sanitizeDatabaseStringContent(&issue.Content)
+}
+
 // LoadTotalTimes load total tracked time
 func (issue *Issue) LoadTotalTimes(ctx context.Context) (err error) {
 	opts := FindTrackedTimesOptions{IssueID: issue.ID}
diff --git a/tests/integration/issue_test.go b/tests/integration/issue_test.go
index 6cb28110969..f6dd99edb52 100644
--- a/tests/integration/issue_test.go
+++ b/tests/integration/issue_test.go
@@ -720,3 +720,15 @@ func TestIssueRefSelectorEnabledForPoster(t *testing.T) {
 	_, hasURL := sel.Attr("data-url-update-issueref")
 	assert.True(t, hasURL, "data-url-update-issueref must be set for the issue poster")
 }
+
+func TestIssueCommentContent(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	issue := &issues_model.Issue{Title: "title\x00content", Content: "body\x00content"}
+	require.NoError(t, db.Insert(t.Context(), issue))
+	unittest.AssertExistsAndLoadBean(t, &issues_model.Issue{ID: issue.ID, Title: "title content", Content: "body content"})
+
+	comment := &issues_model.Comment{Content: "body\x00content"}
+	require.NoError(t, db.Insert(t.Context(), comment))
+	unittest.AssertExistsAndLoadBean(t, &issues_model.Comment{ID: comment.ID, Content: "body content"})
+}